CN101866073A - The drive unit of liquid crystal light modulator and use its variable optical attenuator - Google Patents
The drive unit of liquid crystal light modulator and use its variable optical attenuator Download PDFInfo
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- CN101866073A CN101866073A CN201010163962A CN201010163962A CN101866073A CN 101866073 A CN101866073 A CN 101866073A CN 201010163962 A CN201010163962 A CN 201010163962A CN 201010163962 A CN201010163962 A CN 201010163962A CN 101866073 A CN101866073 A CN 101866073A
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/13306—Circuit arrangements or driving methods for the control of single liquid crystal cells
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
- G09G3/3622—Control of matrices with row and column drivers using a passive matrix
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
- G09G3/3685—Details of drivers for data electrodes
- G09G3/3692—Details of drivers for data electrodes suitable for passive matrices only
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2203/00—Function characteristic
- G02F2203/48—Variable attenuator
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0204—Compensation of DC component across the pixels in flat panels
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/2007—Display of intermediate tones
- G09G3/2014—Display of intermediate tones by modulation of the duration of a single pulse during which the logic level remains constant
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/2007—Display of intermediate tones
- G09G3/2018—Display of intermediate tones by time modulation using two or more time intervals
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
- G09G3/3614—Control of polarity reversal in general
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical & Material Sciences (AREA)
- Theoretical Computer Science (AREA)
- Computer Hardware Design (AREA)
- Nonlinear Science (AREA)
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- Optics & Photonics (AREA)
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- Liquid Crystal Display Device Control (AREA)
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Abstract
The invention provides the drive unit of liquid crystal light modulator and use its variable optical attenuator, and improve the quality of the output light of liquid crystal light modulator.Liquid crystal light modulator (11) is according to the virtual value light modulated of the drive signal of supplying with.Drive unit (21) makes the virtual value of each frame of the drive signal of supplying with to liquid crystal light modulator (11) change according to modulating data.Drive unit (21) is created on the drive signal that contains a plurality of pulses in each frame.Drive unit (21) is supplied with the drive signal that generates to liquid crystal light modulator (11).Thus, can high-frequency drive liquid crystal light modulator (11).
Description
Technical field
The present invention relates to drive the drive unit and the optic modulating device of liquid crystal light modulator.
Background technology
In the past, used the liquid crystal light modulator that utilizes liquid crystal.Variable optical attenuator) liquid crystal light modulator is to utilize (the Variable Optical Attenuator: the element in the purposes such as at VOA.Modulation system as the drive signal of supplying with to liquid crystal light modulator has for example pulse-length modulation (PWM:Pulse Width Modulation: pulse-length modulation).
Pulse-length modulation has easy numerically controlled advantage, and have compare with pulse-height modulation modulation systems such as (PHM:Pulse Height Modulation) circuit scale and consume electric power aspect good advantage.By pulse-length modulation the drive signal of gating pulse width is supplied with to liquid crystal light modulator, thereby can be regulated the attenuation rate of the light in the liquid crystal light modulator and light modulated.Next, the reference clock that drive signal of the prior art and being used to is generated drive signal describes.
Figure 15 is the figure of the existing drive unit of expression to an example of the drive signal of liquid crystal light modulator supply.In Figure 15, the drive signal when pulse width is changed with 32 grades describes.Frame T1 represent the virtual voltage based on modulating data be applied to liquid crystal light modulator liquid crystal light modulator pixel portions during.Reference clock 1510 is for being used to generate the reference clock of drive signal.Frame T1 be clock signal 1510 32 cycles amount during.In addition, after frame T1, set frame T2.At this, the length setting of frame T1 and frame T2 is for equating.
The pulse width modulation precision is stable well carries out in order to make, and pulse width regulating circuit is made of digital circuit usually. Drive signal 1520,1530,1540 is calculated reference clock 1510 according to modulating data and is generated.Shown in the oblique line portion of drive signal 1530,1540, only change 1 as if modulating data, then the corresponding amount of amount of a clock width of pulse width variation and reference clock 1510.Thus, the frequency of reference clock is necessary for more than driving frequency * progression.
Figure 16 is the figure of the existing drive unit of expression to another example of the drive signal of liquid crystal light modulator supply.Drive signal shown in Figure 16 is for to make frequency become 8 times drive signal in drive signal shown in Figure 15.The increase of the caused pulse width of variation of modulating data all is reflected in the pulse.The virtual voltage that applies is identical with drive signal shown in Figure 15.
Patent documentation 1: TOHKEMY 2002-162944 communique
Yet, in existing pulse-length modulation, if in liquid crystal light modulator, use liquid crystal cell to high-speed response, then produce the waveform response (flicker) of liquid crystal cell to the impulse response of drive signal, the problem of deterioration of the output light of liquid crystal light modulator is arranged.To this, though can increase the frame rate of drive signal so that liquid crystal cell not to the impulse response of drive signal, when carrying out Multistage Control, must reduce the minimum pulse width of drive signal.If reduce the minimum pulse width of drive signal, then owing to must increase the frequency of the reference clock that is used to generate drive signal, therefore problems such as the increase of the increase of generation consumption electric power, circuit cost, high frequency interference.
Summary of the invention
The present invention is in order to solve the problem points that above-mentioned prior art produces, and its purpose is, the drive unit and the optic modulating device of the quality of the output light that can improve liquid crystal light modulator is provided.
In order to address the above problem, reach described purpose, drive unit involved in the present invention is supplied with drive signal to the pixel portions of liquid crystal light modulator, this drive unit is characterised in that, described drive signal is made of a plurality of frames, the virtual voltage that described frame is based on modulating data put on described liquid crystal light modulator pixel portions during, described drive unit has the generation mechanism that generates drive signal, this drive signal contains a plurality of pulses in each described frame, described generation mechanism generates following drive signal: when the quantity of the pulse that contains in each described frame does not reach stated number, increase according to described modulating data increases the quantity of the pulse that contains in each described frame, when the quantity of the pulse that contains in each described frame reaches stated number, increase according to described modulating data increases the width of the described pulse that contains in each frame, described drive unit has feed mechanism, and this feed mechanism is supplied with the drive signal that generates mechanism's generation by described to liquid crystal light modulator.
According to said structure, even do not improve the frequency of reference clock, also can be with the liquid crystal light modulator high-frequency drive.And,, the virtual value of each frame of drive signal is changed according to modulating data even do not improve the frequency of reference clock.
And drive unit involved in the present invention is characterised in that in two described frames of front and back, the mode of finishing with alternating polarity generates drive signal.
And drive unit involved in the present invention is characterised in that, described frame with the reference clock that is used to generate described drive signal, interval corresponding with the corresponding umber of pulse of the progression of described modulating data.
And drive unit involved in the present invention is characterised in that, in described frame when applying voltage and be 0V, do not apply between described pulse the most long-term and be set in 1 * 10
-4Below second.
And drive unit involved in the present invention is characterised in that, in described frame when applying voltage and be 0V, do not apply between described pulse the most long-term and be set in 5 * 10
-5Below second.
And drive unit involved in the present invention is characterised in that, the low-limit frequency that contains in the drive signal of the inverse definition in the frame alternating polarity cycle when reaching stated number by the quantity of the pulse that contains in each described frame is more than the 100Hz.
In addition, variable optical attenuator involved in the present invention is characterised in that to have the drive unit of above-mentioned liquid crystal light modulator.
According to said structure,, the virtual value of each frame of drive signal is changed according to modulating data even do not improve the frequency of reference clock.
The invention effect
According to drive unit involved in the present invention and optic modulating device, can reach the effect of the quality raising of the output light that makes liquid crystal light modulator.
Description of drawings
Fig. 1-the 1st, the block diagram of the structure of the drive unit that the expression embodiment is related.
Fig. 1-2 is the block diagram of the variation of the drive unit shown in the presentation graphs 1-1.
Fig. 2 is the figure of the drive unit shown in presentation graphs 1-1 or Fig. 1-2 to an example of the drive signal of liquid crystal light modulator supply.
Fig. 3 is the block diagram of the concrete structure example of the segment drive circuit shown in presentation graphs 1-1 or Fig. 1-2.
Fig. 4 is the figure of the output waveform of expression frequency dividing circuit shown in Figure 3.
Fig. 5 is the circuit diagram of the concrete structure example of expression multiple-pulse circuit shown in Figure 3.
Fig. 6 is the figure of the output waveform of expression multiple-pulse circuit (second path) shown in Figure 5.
Fig. 7 is the circuit diagram of the concrete structure example of expression first output circuit shown in Figure 3.
Fig. 8 is the figure of the output waveform of expression first output circuit shown in Figure 7.
Fig. 9-the 1st, the figure of the waveform of the voltage that expression applies each electrode of liquid crystal light modulator.
Fig. 9-the 2nd, expression is to the figure of the waveform of the actual voltage that applies of the liquid crystal layer of liquid crystal light modulator.
Fig. 9-the 3rd, the figure of the variation of the output light intensity of expression liquid crystal light modulator.
Figure 10 is the light intensity characteristic of expression when using liquid crystal light modulator as VOA and the chart of an example of waveform response characteristic.
Figure 11 be the maximum waveform response of expression than with the chart of the relation of regeneration frequency.
Figure 12-the 1st, the figure of the experimental circuit of Vcom conversion is estimated in expression.
Figure 12-the 2nd, the figure of the driving voltage that expression applies the liquid crystal light modulator shown in Figure 12-1.
Figure 12-the 3rd, the figure of the optic response that expression is monitored by the wave detector shown in Figure 12-1.
Figure 13 is an expression direct current offset chart over time.
Figure 14 is the chart of an example of the dielectric property of expression liquid crystal material 5CB.
Figure 15 is the figure of the existing drive unit of expression to an example of the drive signal of liquid crystal light modulator supply.
Figure 16 is the figure of the existing drive unit of expression to another example of the drive signal of liquid crystal light modulator supply.
Among the figure: the T1-frame; 11,911,1211-liquid crystal light modulator; 12,13-substrate; The 14-common electrode; The 15-segment electrode; 16,17-polarization plates; The 18-seal; The 19-liquid crystal; The 21-drive unit; 511～515-, first input part～the 5th input part; 521～525-, first change-over switch～the 5th change-over switch; 531～535-, first efferent～the 5th efferent; 711～716-input part; 721～725-storer; 731～735,761～765-OR circuit; 741～745,751～755-"AND" circuit; The 770-"or" else circuit; The 780-impact damper; The 790-efferent; 912,913-electrode; 1010-waveform response characteristic; 1020-light intensity characteristic; The 1212-power supply; The outside DC power supply of 1213-; The 1214-catoptron; The 1215-wave detector; 1221-rectangle alternating voltage; 1222,1223-optic response; 1410-dielectric relaxation curve.
Embodiment
Below the suitable embodiment of present invention will be described in detail with reference to the accompanying related drive unit and light adjusting gear.
(embodiment)
(structure of drive unit)
Fig. 1-the 1st, the block diagram of the structure of the drive unit that the expression embodiment is related.Liquid crystal light modulator 11 shown in Fig. 1-1 constitutes, constitute by glass or silicon-be respectively arranged with common electrode 14 and segment electrode 15 on the face opposite one another to substrate 12,13, and on the face of opposition side, be respectively arranged with polarization plates 16,17.And, in by described substrate 12,13 and seal 18 sealed space, be incorporated with liquid crystal 19.
To drive unit 21 input modulating datas (level data).Drive unit 21 makes each virtual value to the frame correspondence of the segment signal (drive signal) of liquid crystal light modulator 11 supplies change according to modulating data.Frame (Off レ one system) be meant the virtual voltage based on modulating data put on the pixel during (Qi Inter), be the control unit of optical modulation.For example, frame is the interval of umber of pulse of the progression of reference clock, corresponding modulating data.At this moment, frame be make the variable quantity of pulse width of the drive signal after modulating data changes 1 grade continuous the interval of amount of progression.Beyond removing when having changed modulating data, the effective value of frame is fixed.Drive unit 21 comprises: segment drive circuit 22, co-driver 23, control circuit 24, analog power circuit 25.
24 pairs of segment drive circuits of control circuit 22 are supplied with reference clock, the sequential when pulse-length modulation is carried out in this reference clock control.In addition, 24 pairs of co-drivers of control circuit 23 are supplied with polar signal.25 pairs of segment drive circuits 22 of analog power circuit and co-driver 23 are supplied with the DC voltage that is used to carry out voltage amplification.The DC voltage that segment drive circuit 22 and co-driver 23 are supplied with according to analog power circuit 25 respectively, and generation is applicable to the segment signal and the common signal of the voltage level of liquid crystal drive.
Fig. 1-2 is the block diagram shown in the variation of the drive unit shown in the presentation graphs 1-1.Shown in Fig. 1-2, liquid crystal light modulator 11 also can be formed by reflection-type.At this moment, polarization plates only is disposed at substrate 12 sides (polarization plates 16), and making segment electrode 15 is by the film formed reflective electrode of the metal of high reflectances such as Al.
(example of drive signal)
Fig. 2 is the figure of the drive unit shown in presentation graphs 1-1 or Fig. 1-2 to an example of the drive signal of liquid crystal light modulator supply.In Fig. 2, the pulse width that the makes drive signal situation with 32 grades of variations is described.Frame T1, T2 represent during liquid crystal light modulator 11 applies based on the virtual voltage of modulating data.At this, with the length setting of frame T1 and frame T2 for equating.Reference clock 210 is the reference clock of supplying with to segment drive circuit 22 from control circuit 24.Frame T1, T2 be reference clock 210 32 periodic quantities during.
Drive signal 220 is to become the drive signal that 6/32 grade mode generates with pulse width.Drive signal 230 is to become the drive signal that 7/32 grade mode generates with pulse width.Drive signal 240 is to become the drive signal that 8/32 grade mode generates with pulse width.Shown in drive signal 220,230,240, the segment drive circuit 22 of drive unit 21 generates the drive signal that contains a plurality of pulses in each frame.
In addition, the segment drive circuit 22 of drive unit 21 is created on the drive signal of the pulse of the quantity that contains with good grounds modulating data in each frame.Specifically, drive signal 220 contains six pulses in each frame, and drive signal 230 contains seven pulses in each frame, and drive signal 240 contains eight pulses in each frame.So, the increase according to modulating data increases the umber of pulse that contains in each frame.
For example, as shown in Figure 2, in segment drive circuit 22, if make modulating data increase one-level from the state that generates drive signal 240, the drive signal 250 that the width that then produces the 8th pulse 251 that makes initial frame T1 increases and the width of the 8th pulse 252 of next frame T2 is increased.And, in segment drive circuit 22, if make modulating data increase one-level from the state that generates drive signal 250, the drive signal 260 that the width that then produces the 7th pulse 261 that makes initial frame T1 increases and the width of the 7th pulse 262 of second frame T2 is increased.
Like this, drive unit 21 is created on the multiple-pulse driving of the drive signal that contains a plurality of pulses in each frame.And, in drive unit 21, by increase the quantity of the pulse that contains in each frame is increased, thereby control is according to the virtual value of the drive signal of modulating data according to modulating data.In addition, in drive unit 21, the width of the pulse that contains in each frame is increased, thereby control is according to the virtual value of the control signal of modulating data.
And as shown in Figure 2, in drive unit 21, the quantity of the pulse that contains in each frame does not reach under the situation of stated number (is eight at this), and the quantity of the pulse that contains in each frame is increased.At this moment, in drive unit 21, the quantity of the pulse that contains in each frame reaches under the situation of stated number, makes the width increase of the pulse that contains among each frame T1 according to the increase of modulating data.
In the multiple-pulse of utilizing this drive unit 21 to carry out drives, owing to contain a plurality of pulses in each frame, therefore can be with liquid crystal light modulator 11 high-frequency drive.Thus, when the virtual value of each frame that obtains regulation, can shorten consecutive pulses at interval.Because the pulse-shape response when using the liquid crystal material of high-speed response type in liquid crystal light modulator 11 extremely depends on the recurrent interval, therefore drives by carrying out such multiple-pulse, also can the suppressor pulse waveform response even do not improve frame frequency.
And,, the frequency of the reference clock of the resolution that determines drive signal is reduced owing to can not improve frequency.Therefore, can realize the minimizing of low consumption electrification and high frequency interference.
In Fig. 2, two frames are described, i.e. the frame T2 of the frame T1 of first half and latter half.The frame T1 of first half all is made of the pulse of positive voltage.And the T2 of the frame of latter half all is made of the pulse of negative voltage.Thus, put upside down at two frame Semi-polarities.Because two frames are all identical except that polarity, therefore the virtual value of two frames equates.Because the frame of polarity reversal is continuous like this, therefore positive and negative voltage offset in two frames need not to apply direct current (DC).But, under the situation after frequency is reduced,, produce the influence of the DC skew that causes by mobile ion and the reliability decrease of optic modulating device even be that 0 mode drives with DC quantity.Thus, preferably drive, describe in detail in the back on the one hand about this with high-frequency.
(the concrete structure example of segment drive circuit)
Fig. 3 is the block diagram of the concrete structure example of the segment drive circuit shown in presentation graphs 1-1 or Fig. 1-2.As shown in Figure 3, segment drive circuit 22 (with reference to Fig. 1-1 or Fig. 1-2) has: frequency dividing circuit 310, multiple-pulse circuit 320, first output circuit 331 and second output circuit 332.The reference clock that 310 inputs are supplied with by control circuit 24 to frequency dividing circuit.
To each signal and the modulating data of first output circuit, 331 inputs from 320 outputs of multiple-pulse circuit.First output circuit 331 will be modulated based on modulating data from each signal of multiple-pulse circuit 320 outputs, and the signal after the modulation is exported as drive signal.To each signal and the modulating data of second output circuit, 332 inputs from 320 outputs of multiple-pulse circuit.Second output circuit 332 will be modulated based on modulating data from each signal of multiple-pulse circuit 320 outputs, and the signal after the modulation is exported as drive signal.
In addition, thus in this explanation the structure that first output circuit 331 and second output circuit 332 are exported two drive signals is set.To this, when the drive signal of necessity is one, also can adopt the structure of omitting second output circuit 332.And, be three when above in the drive signal of necessity, also can adopt the structure that is provided with three above output circuits.Thus, when each electrode in a plurality of segment electrodes is used different drive signals, only need to be provided with the output circuit of segment electrode number.
Fig. 4 is the figure of the output waveform of frequency dividing circuit shown in Figure 3.As shown in Figure 4, frequency dividing circuit 310 (with reference to Fig. 3) output: first fractional frequency signal 410 (Q1), second fractional frequency signal 420 (Q2), three frequency division signal 430 (Q3), the 4th fractional frequency signal 440 (Q4), the 5th fractional frequency signal 450 (Q5).First fractional frequency signal 410 is and the identical fractional frequency signal of importing to frequency dividing circuit 310 of reference clock frequency.Second fractional frequency signal 420 is the fractional frequency signals to 1/2 frequency of the frequency of the reference clock of frequency dividing circuit 310 input.
Three frequency division signal 430 is the fractional frequency signals to 1/4 frequency of the frequency of the reference clock of frequency dividing circuit 310 input.The 4th fractional frequency signal 440 is the fractional frequency signals to 1/8 frequency of the frequency of the reference clock of frequency dividing circuit 310 input.The 5th fractional frequency signal 450 is the fractional frequency signals to 1/16 frequency of the frequency of the reference clock of frequency dividing circuit 310 input.
Fig. 5 is the circuit diagram of the concrete structure example of expression multiple-pulse circuit shown in Figure 3.As shown in Figure 5, multiple-pulse circuit 320 has: first input part 511～the 5th input part 515, first change-over switch 521～the 5th change-over switch 525, first efferent 531～the 5th efferent 535, not shown switch control portion.
The 3rd input part 513 is exported the fractional frequency signal (Q3) of input respectively to the 3rd change-over switch 523 and the 5th change-over switch 535.The 4th input part 514 is exported the fractional frequency signal (Q4) of input respectively to the 4th change-over switch 524 and first change-over switch 521.The 5th input part 515 is exported the fractional frequency signal (Q5) of input respectively to the 5th change-over switch 525 and second change-over switch 522.
First change-over switch 521 is switched first path and second path mutually, and this first path will be exported to first efferent 531 from the signal of first input part, 511 outputs, and this second path will be exported to first efferent 531 from the signal of the 4th input part 514 outputs.Second change-over switch 522 is switched first path and second path mutually, and this first path will be exported to second efferent 532 from the signal of second input part, 512 outputs, and this second path will be exported to second efferent 532 from the signal of the 5th input part 515 outputs.
The 3rd change-over switch 523 is switched first path and second path mutually, and this first path will be exported to the 3rd efferent 533 from the signal of the 3rd input part 513 outputs, and this second path will be exported to the 3rd efferent 533 from the signal of first input part, 511 outputs.The 4th change-over switch 524 is switched first path and second path mutually, and this first path will be exported to the 4th efferent 534 from the signal of the 4th input part 514 outputs, and this second path will be exported to the 4th efferent 534 from the signal of second input part, 512 outputs.
The 5th change-over switch 525 is switched first path and second path mutually, and this first path will be exported to the 5th efferent 535 from the signal of the 5th input part 515 outputs, and this second path will be exported to the 5th efferent 535 from the signal of the 3rd input part 513 outputs.First efferent 531～the 5th efferent 535 respectively will be from the signal (P1～P5) export to first output circuit 331 and second output circuit 332 of first change-over switch 521～the 5th change-over switch 525 outputs.Switch control portion is so that first change-over switch 521～the 5th change-over switch 525 becomes the mode in first path or second path controls.
By by switch control portion so that first change-over switch 521～the 5th change-over switch 525 becomes the mode in first path controls, do not change order and export to each fractional frequency signal of multiple-pulse circuit 320 inputs from frequency dividing circuit 310.And, by by switch control portion so that first change-over switch 521～the 5th change-over switch 525 becomes the mode in second path controls, export to each fractional frequency signal transposing orders of multiple-pulse circuit 320 inputs from frequency dividing circuit 310.
Output waveform at the multiple-pulse circuit 320 of first change-over switch 521～when the 5th change-over switch 525 becomes first path respectively is identical with output waveform shown in Figure 4, therefore omits explanation.Owing to by making first change-over switch 521～the 5th change-over switch 525 become first path each signal is not changed, therefore can be created on the drive signal that contains a pulse in each frame.Thus, can generate the suitable drive signal of the characteristic of corresponding for example purposes or liquid crystal.
In addition, when containing the drive signal of a plurality of pulses in generating each frame, the switch control portion of multiple-pulse circuit 320 is so that first change-over switch 521～the 5th change-over switch 525 becomes the mode in second path controls.The output waveform of explanation multiple-pulse circuit 320 at this moment in Fig. 6.In addition, in multiple-pulse circuit 320 shown in Figure 5, employing can be selected not change each signal and export or change each signal and the structure exported, but multiple-pulse circuit 320 adopts the structure of changing each signal all the time and exporting.
Fig. 6 is the figure of the output waveform of expression multiple-pulse circuit (second path) shown in Figure 5.First output signal 610 shown in Figure 6 is the signal (P1) from first efferent, 531 outputs of multiple-pulse circuit 320, and is identical with the 4th fractional frequency signal 440 shown in Figure 4.Second output signal 620 is from the signal (P2) of second efferent, 532 outputs of multiple-pulse circuit 320, and is identical with the 5th fractional frequency signal 450 shown in Figure 4.
The 3rd output signal 630 is the signal (P3) from the 3rd efferent 533 outputs of multiple-pulse circuit 320, and is identical with first fractional frequency signal 410 shown in Figure 4.The 4th output signal 640 is the signal (P4) from the 4th efferent 534 outputs of multiple-pulse circuit 320, and is identical with second fractional frequency signal 420 shown in Figure 4.
The 5th output signal 650 is the signal (P5) from the 5th efferent 535 outputs of multiple-pulse circuit 320, and is identical with three frequency division signal 430 shown in Figure 4.So, first change-over switch 521～the 5th change-over switch 525 output signal of becoming the multiple-pulse circuit 320 in second path becomes the signal with each fractional frequency signal transposing shown in Figure 4.At this, frequency dividing circuit 310 each output order by the multiple-pulse circuit 320 each two change.
Fig. 7 is the circuit diagram of the concrete structure example of expression first output circuit shown in Figure 3.As shown in Figure 7, first output circuit 331 (with reference to Fig. 3) comprising: input part 711～716, storer 721～725, OR circuit 731～735, "AND" circuit 741～745, "AND" circuit 751～755, "AND" circuit 761～765, "or" else circuit 770, impact damper 780, efferent 790.
If modulating data is 5 (0～31), everybody is D1～D5, then stores D1～D5 in storer 721～725 respectively.For example, if the value of modulating data is 2 (binary number is 00010), then store 0,1,0,0,0 in the storer 721～725 respectively.In addition, if the value of modulating data is 3 (binary number is 00011), then store 1,1,0,0,0 in the storer 721～725 respectively.
To the signal (P1) of input part 711 inputs from first efferent, 531 outputs of multiple-pulse circuit 320.Input part 711 is exported the signal of input to OR circuit 731 and "AND" circuit 751.OR circuit 731 will represent from the signal of input part 711 output and the logic that is stored in the modulating data (D1) the storer 721 and signal to "AND" circuit 741 outputs.
An input of "AND" circuit 741 is connected with OR circuit 731, another the input by on draw.Therefore, at least one of the modulating data of storing signal of exporting from first efferent 531 (P1) and storer 721 (D1) is 1 o'clock, and OR circuit 731 is output as 1, and "AND" circuit 741 is output as 1.The modulating data (D1) of storage is 0 o'clock signal of exporting from first efferent 531 (P1) and storer 721, and OR circuit 731 is output as 0, and "AND" circuit 741 is output as 0.
"AND" circuit 751 will represent that the signal of the logic product of the modulating data of storage from the signal of input part 711 outputs and storer 721 is to OR circuit 761 outputs.OR circuit 761 will represent from the signal of "AND" circuit 741 output and from the logic of the signal of "AND" circuit 751 outputs and signal to "AND" circuit 742 outputs.
To the signal (P2) of input part 712 inputs from second efferent, 532 outputs of multiple-pulse circuit 320.Input part 712 is exported the signal of input to OR circuit 732 and "AND" circuit 752.OR circuit 732 will represent the modulating data (D2) of storage from the signal of input part 712 output and storer 722 logic and signal export to "AND" circuit 742."AND" circuit 742 will be represented to export to OR circuit 762 with the signal of the logic product of the signal of exporting from OR circuit 732 from the signal of OR circuit 761 outputs.
"AND" circuit 752 will represent that the signal of the logic product of the modulating data of storage from the signal of input part 712 outputs and storer 722 is to OR circuit 762 outputs.OR circuit 762 will represent from the signal of "AND" circuit 742 output with from the logic of the signal of "AND" circuit 752 outputs and signal to "AND" circuit 743 outputs.
To the signal (P3) of input part 713 inputs from the 3rd efferent 533 outputs of multiple-pulse circuit 320.Input part 713 is exported the signal of input to OR circuit 733 and "AND" circuit 753.OR circuit 733 will represent the modulating data (D3) of storage from the signal of input part 713 output and storer 723 logic and signal export to "AND" circuit 743."AND" circuit 743 will be represented to export to OR circuit 763 with the signal of the logic product of the signal of exporting from OR circuit 733 from the signal of OR circuit 762 outputs.
"AND" circuit 753 will represent that the signal of the logic product of the modulating data of storage from the signal of input part 713 outputs and storer 723 is to OR circuit 763 outputs.OR circuit 763 will represent from the signal of "AND" circuit 743 output with from the logic of the signal of "AND" circuit 753 outputs and signal to "AND" circuit 744 outputs.
To the signal (P4) of input part 714 outputs from the 4th efferent 534 outputs of multiple-pulse circuit 320.Input part 714 is exported the signal of input to OR circuit 734 and "AND" circuit 754.OR circuit 734 will represent the modulating data (D4) of storage from the signal of input part 714 output and storer 724 logic and signal export to "AND" circuit 744."AND" circuit 744 will be represented to export to OR circuit 764 with the signal of the logic product of the signal of exporting from "AND" circuit 734 from the signal of OR circuit 763 outputs.
"AND" circuit 754 will represent that the signal of the logic product of the modulation signal (D4) of storage from the signal of input part 714 outputs and storer 724 is to OR circuit 764 outputs.OR circuit 764 will represent from the signal of "AND" circuit 744 output with from the logic of the signal of "AND" circuit 754 outputs and signal to "AND" circuit 745 outputs.
To the signal (P5) of input part 715 inputs from the 5th efferent 535 outputs of multiple-pulse circuit 320.Input part 715 is exported the signal of input to OR circuit 735 and "AND" circuit 755.OR circuit 735 will represent the modulation signal (D5) of storage from the signal of input part 715 output and storer 725 logic and signal export to "AND" circuit 745."AND" circuit 745 will be represented to export to OR circuit 765 with the signal of the logic product of the signal of exporting from OR circuit 735 from the signal of OR circuit 764 outputs.
"AND" circuit 755 will represent that the signal of the logic product of the modulation signal (D5) of storage from the signal of input part 715 outputs and storer 725 is to OR circuit 765 outputs.OR circuit 765 will represent from the signal of "AND" circuit 745 output with from the logic of the signal of "AND" circuit 755 outputs and signal to "or" else circuit 770 outputs.
To input part 716 input polar signal Po1.Input part 716 is exported the polar signal Po1 of input to "or" else circuit 770."or" else circuit 770 will be represented to export to impact damper 780 with the signal of the addition without carry of the signal Po1 that exports from input part 716 from the signal of OR circuit 765 outputs.Impact damper 780 will be from the signal amplification of "or" else circuit 770 output and to efferent 790 outputs.
Fig. 8 is the figure of the output waveform of expression first output circuit shown in Figure 7.At modulating data n is 1 o'clock, and drive signal 801 shown in Figure 8 is the drive signal from 1 frame of first output circuit, 331 outputs.Similarly, be 2～12 o'clock at modulating data n, drive signal 802～812 is respectively from the drive signal of 1 frame of output circuit output.
As shown in Figure 8, the quantity of the pulse that contains in each frame is less than 4 o'clock, the increase of drive unit 21 corresponding modulating data n and the quantity of the pulse that contains in each frame is increased.And the quantity of the pulse that contains in each frame reaches at 4 o'clock, the increase of drive unit 21 corresponding modulating data n and the width of the pulse that contains in each frame is increased.
And, when the width that makes pulse increases, the every increase by 1 of modulating data n, then drive unit 21 increases the width of a pulse in each pulse that contains in the frame.In Fig. 8, be that the situation of 1～12 o'clock first efferent 531 output is illustrated to the modulation data n, modulating data n is 13～31 o'clock, the every increase by 1 of modulating data n, the drive signal that pulse width has increased is just exported from first efferent 531.
(waveform response)
Next, the waveform response (flicker) that can reduce by the related drive unit 21 of embodiment is described.As shown in Figure 2, if be conceived to drive signal 220, then exist do not apply in the frame pulse during.If this do not apply pulse during elongated, then remove when applying voltage and being 0V, just remove the situation that off-set value is 0V, liquid crystal layer responds, waveform response (flicker) becomes greatly.
At this, observe out from this pulse be applied to that next pulse is applied in during between (regeneration period) the most long-term, the drive waveforms that waveform response (flicker) diminishes is discussed.In the above description, the frame T1 of first half and polarity reversal have been described the multiple-pulse of the present invention of frame T2 of latter half drive the example of method, but in this, for the waveform response of liquid crystal is described, the waveform of simple pulse-length modulation that the frame T2 of the frame T1 of first half and latter half is made polarity reversal respectively as a pulse is as example.
Fig. 9-the 1st, the figure of the waveform of the voltage that expression applies each electrode of liquid crystal light modulator.In Fig. 9-1, transverse axis express time [ms], the longitudinal axis is represented voltage V[V].Liquid crystal light modulator 911 expressions are supplied with the liquid crystal light modulator of drive signal to it.Liquid crystal light modulator 911 is a nematic crystal.The variation of the voltage that waveform 914 expression of Fig. 9-1 applies to the electrode 912 of liquid crystal light modulator 911.The variation of the voltage that waveform 915 expression applies to the electrode 913 of liquid crystal light modulator 911.
Fig. 9-the 2nd, expression is to the figure of the waveform of the actual voltage that applies of the liquid crystal layer of liquid crystal light modulator.In Fig. 9-2, transverse axis express time [ms], the longitudinal axis is represented voltage V[V].When the waveform 921 of Fig. 9-2 is illustrated in the electrode 912 of liquid crystal light modulator 911 and electrode 913 is applied voltage shown in Fig. 9-1, to the variation of the actual voltage that applies of the liquid crystal layer of liquid crystal light modulator 911, be equivalent to the waveform 914 of Fig. 9-1 and the synthetic waveform of waveform 915.
The pulse width of the voltage that symbol 922 expression applies the liquid crystal layer of liquid crystal light modulator 911.The drive cycle (T) of the voltage that symbol 923 expression applies the liquid crystal layer of liquid crystal light modulator 911.In Fig. 9-2, to the frame T2 of the frame T1 of first half and latter half respectively with make polarity reversal as a pulse the waveform of simple pulse-length modulation be example.
At this,, be a frame during to the applying of next negative pulse during therefore from the applying of positive pulse based on applying owing to implement of the virtual voltage of a modulating data by a pulse.Thus, the drive cycle T in Fig. 9-2 is equivalent to the twice of a frame.The regeneration period of the voltage that symbol 924 expression applies the liquid crystal layer of liquid crystal light modulator 911, specifically, from applying pulse during apply next pulse.
Fig. 9-the 3rd, the figure of the variation of the output light intensity of expression liquid crystal light modulator.In Fig. 9-3, transverse axis represents to apply [ms], and the longitudinal axis is represented light intensity (arbitrary unit).One example of the variation of the output light intensity of the liquid crystal light modulator 911 when waveform 931 expression of Fig. 9-3 applies voltage shown in Fig. 9-2 to the liquid crystal layer of liquid crystal light modulator 911.
The intensity variation of the output light of the pairing liquid crystal light modulator 911 of symbol 932 indicating impulse width.The pairing regeneration period of regeneration period of the output light of symbol 933 expression liquid crystal light modulators 911.The amplitude of fluctuation of the pairing light intensity of waveform response of the output light of symbol 934 expression liquid crystal light modulators 911.If by the ejaculation light of photodetector (PD:Photo Detector) detection liquid crystal light modulator, then the ejaculation light owing to liquid crystal light modulator is output as magnitude of voltage, so the changing voltage amplitude Vp_p of the amplitude of fluctuation of this light intensity and PD is proportional.The mean value of the output light of symbol 935 expression liquid crystal light modulators 911, proportional with the average voltage Vdc of photodetector (PD).
Liquid crystal cells such as nematic crystal are the virtual value response.The virtual value Vrms of driving voltage V can be represented by following formula (1).In following formula (1), T represents the drive cycle (T) shown in the symbol 923 of Fig. 9-2 for example, and the voltage shown in the longitudinal axis of V presentation graphs 9-2, t0 are represented the rise time of the pulse of voltage that liquid crystal layer is applied.
[formula 1]
But, shown in Fig. 9-3, the high speed liquid crystal light modulator of high-speed response to each impulse response, as waveform response (flicker), is occurred with actual the control signal of the liquid crystal layer digital interference that it doesn't matter (Digital Artifact).When using at the variable optical attenuator that liquid crystal light modulator is used as optical communication (VOA:Variable Optical Attenuator), such flicker effects is exported the quality of light or is built-in with the characteristic of the communication of liquid crystal light modulator with assembly.Therefore, preferred consideration reduces this flicker.Next, the quantitative evaluation method that this waveform is replied describes.
Figure 10 is the light intensity characteristic of expression when liquid crystal light modulator used as VOA and the chart of an example of waveform response characteristic.At this, the liquid crystal light modulator that uses as VOA adopts following parallel-oriented liquid crystal cell, it is an infiltration type and with the polarization axle configured in parallel of a pair of polarization plates, and the director orientation of liquid crystal (ダ イ レ Network タ direction) is set at and sees through axle 45 degree that tilt with respect to polarization plates.In addition, the cell gap of this liquid crystal light modulator is 10 μ m, and liquid crystal material uses the MJ011580 of Merck ﹠ Co., Inc. (Merck Ltd.).
In Figure 10, transverse axis is represented the virtual value [Vrms] of driving voltage, and the longitudinal axis in left side is represented the average voltage Vdc[V with the proportional photodetector of ejaculation light intensity of VOA].The longitudinal axis on right side represents to illustrate the residual waveform response of degree of overlapping of waveform response (flicker) than (RWR:Residual Waveform Response Ratio).This residual waveform response shows big value than more, and it is obvious more to glimmer.1010 expressions of waveform response characteristic are with respect to the characteristic of the residual waveform response ratio of the virtual value of driving voltage.1020 expressions of light intensity characteristic are with respect to the characteristic of the average voltage Vdc of the pairing photodetector of light intensity of the virtual value of driving voltage.
Light intensity characteristic and waveform response characteristic when in addition, 1020 expressions of the waveform response characteristic 1010 of Figure 10 and light intensity characteristic apply the driving voltage of PWM (pulse-length modulation) waveform to VOA.In this example, the frequency of drive signal is 1kHz (regeneration frequency is 2kHz), and finding speed is 10[℃], the mensuration wavelength is 1550nm.
The average voltage Vdc of photodetector is converted to the value that voltage reads by oscillograph for the output of the photodetector (PD) of the output light sensation light that will make VOA.Because the output of PD and the light intensity of sensitization are proportional, so the output of PD can consider to adopt the output light intensity shown in Fig. 9-3.The output of the voltage of PD with the proportional zone of light intensity in measure.At this, residual waveform response defines suc as formula (2) than RWR.
Formula (2)
At this, Ip_p is the variation of the light intensity that causes of waveform response, is equivalent to the symbol 934 of Fig. 9-3, and Idcmax is maximum average luminous intensity.In addition, Vp_p is the changing voltage of the PD that causes of waveform response, and Vp_p (0) is 0[Vrms for virtual value] time the changing voltage of PD.At this, virtual value is 0[Vrms on principle] time, the change that should not have waveform response to cause, but owing to interference or the fluctuating of PD produces Vp_p (0).
Thus, for the size of the actual effect that calculates Ip_p, make changing voltage Vp_p deduct the value (Vp_p-Vp_p (0)) of Vp_p (0) as variation caused with the waveform response of PD and the proportional voltage of light intensity.And, the average output voltage of the PD when Vdcmax becomes maximum for the average voltage by photodetector output.
At this, the size of the degree of the waveform response characteristic of Figure 10 1010 expression flickers, and waveform response characteristic 1010 has peak value between the maximal value of light intensity characteristic 1020 and minimum value.Can think this be because, when the driving voltage of PWM hangs down, little and the waveform response of the action of liquid crystal molecule is originally just little, and when the driving voltage of PWM is high, and therefore influence waveform response is difficult to manifest that waveform response diminishes because the interval between the PWM waveform is narrow.
In the condition of Figure 10, when the driving voltage of PWM hangs down, because the relation of the initial delay of liquid crystal is not 0 from initial light intensity, the incident polarized light rotation pi/2 that when being about to surpass 2V, penetrates from the incident polarization plate and become closure state with emitting side polarizer quadrature, light intensity approaches 0.Therefore, on the waveform response family curve, near 2V, also can observe little peak value.
At this, for the experimental optimal regeneration period of determining as the pulse of drive signal, define as shown in the formula (3) than RWM with the maximum waveform response of taking the logarithm as the maximal value of RWR as the maximal value of the residual waveform response ratio of this index.We can say that maximum waveform response is more littler than RWM, the degree of flicker is more little.In following formula (3), the residual waveform response when maximum waveform response is got maximal value than RWM by waveform response characteristic 1010 is obtained than the value of RWRmax.
Formula (3)
RWM＝10log
10RWRmax …(3)
Can learn by Figure 10, in the actuating range of liquid crystal light modulator, because when residual waveform response reaches maximum RWRmax than the value of RWR, therefore the influence of waveform response (degree of flicker) maximum is the waveform that index is studied drive signal with the maximum waveform response of being taken the logarithm by this RWRmax after calculating than RWR.
Figure 11 be the maximum waveform response of expression than with the chart of the relation of regeneration frequency.At this, the regeneration period is represented the cycle of regeneration period with frequency.Regeneration period as mentioned above, for from apply pulse to apply next pulse during, in Figure 11, transverse axis is represented the regeneration frequency [Hz] of drive signal, the longitudinal axis represents that the maximum waveform response of following formula (3) is than RWM[dB].Characteristic 1111～1115 represents that respectively operating temperature is-7[℃], 10[℃], 25[℃], 50[℃], 70[℃] time with respect to the maximum waveform response of regeneration frequency characteristic than RWM.
When each operating temperature, the big more then maximum waveform response of regeneration frequency is more littler than RWM as can be known.And, even the identical RWM of the high more regeneration frequency of temperature is also big more as can be known.In addition, result shown in Figure 11 is, owing to constitute VOA by the liquid crystal light modulator of infiltration type, the interference level of mensuration system that is used for this mensuration is at-30[dB] near, so each curve is at-30[dB] near asymptotic.
If make operating temperature from-7[℃] to 70[℃], then as can be known by result shown in Figure 11, for maximum waveform response for example is suppressed at-25[dB than RWM] below, consider that exacting terms is 70[℃] time, regeneration frequency is necessary for 10000[Hz] (10[kHz]) more than.And, as can be known because the interference level of measuring system at-30[dB] near, so considering its background interference, with 70[℃] the regeneration frequency of figure during from the characteristic of lower curve extrapolation (dotted line that the characteristic 1115 of Figure 11 is prolonged), for maximum waveform response is suppressed at-30[dB than RWM] below, must make regeneration frequency is about 21[kHz] more than.
In addition,, use to seeing through polarized light dependent form and cell gap to be 10[μ m at this] liquid crystal light modulator, use the 5[V that generates by pulse-length modulation] drive signal.Usually, if the situation that liquid crystal light modulator of the present invention is used as VOA, then be set at 0 in the damping capacity scope of VOA～-20[dB] time, waveform response (flicker) if suppress for RWM-25～-30[dB] can be regarded as practicality with next.
Thus, regeneration frequency is preferably set to 10[kHz] more than, more preferably be set at about 21[kHz in other words] more than.That is to say, if consider to be applicable to driving method of the present invention, when then removing in frame applies voltage and is 0V, do not apply between voltage the most long-term if get final product, so be set at 1 * 10 with the corresponding inverse of then getting frequency of waveform that this has illustrated
-4[second] (=1/10[kHz]) below, be preferably set to 5 * 10
-5[second] (≈ 1/21[kHz]) below.
(Vcom conversion)
Figure 12-the 1st, the experimental circuit of Vcom conversion is estimated in expression.Liquid crystal light modulator 1211 shown in Figure 12-1 is the VOA of the liquid crystal light modulator of use reflection-type.Power supply 1212 is supplied with driving voltage to liquid crystal light modulator 1211.1213 pairs of liquid crystal light modulators 1211 of outside DC power supply apply DC voltage.Catoptron 1214 makes incident light to liquid crystal light modulator 1211 reflections.Wave detector 1215 (DET) is monitoring by catoptron 1214 reflection and by the photodetector (PD) of the light of liquid crystal light modulator 1211 reflections.
Figure 12-the 2nd, the figure of the driving voltage that expression applies the liquid crystal light modulator shown in Figure 12-1.In Figure 12-2, transverse axis express time, the longitudinal axis are represented the voltage that applies to liquid crystal light modulator 1211.Shown in Figure 12-2, illustrate by 1212 pairs of liquid crystal light modulators 1211 of power supply to apply the situation that dutycycle is 0.5 rectangle alternating voltage 1211.
Figure 12-the 3rd, expression is by the figure of the optic response of the monitoring of the wave detector shown in Figure 12-1.In Figure 12-3, transverse axis express time, the longitudinal axis are represented the optic response of liquid crystal light modulator 1211.Optic response by wave detector 1215 monitoring in the ideal case with the situation equivalence that in the experimental provision shown in Figure 12-1, does not have outside DC power supply 1213, be what fix as the optic response of Figure 12-3.This be because, owing to be the virtual value response as the liquid crystal light modulator 1211 of nematic crystal unit, therefore original optic response with respect to electric field alternately just for fixing.
But, in the mensuration of reality, driving under (several hertz～tens hertz) at low frequency, the optic response of monitoring by wave detector 1215 becomes as the optic response among Figure 12-3 1223, and the generation of the flicker of rectangle alternating voltage 1221 correspondences can be observed mostly.At this moment, should be noted that it is different with the flicker of the described waveform response that applies pulse waveform of reflection, can observedly glimmer along with the polarity reversal of low frequency drive waveforms.Its reason is, forms a part of mobile ionization of foreign ion of the asymmetry of component structure of liquid crystal light modulator 1211 or liquid crystal inside and the skew of the space charge that produces.
Under the situation that produces such flicker since with the situation equivalence that liquid crystal layer inside is applied DC voltage, therefore influence long-term reliability, become the main cause of the deterioration that causes device characteristics.Vcom (common voltage) conversion be so that flicker can't observed mode apply DC voltage (bias voltage) by outside DC power supply 1213 from the outside, at this moment DC voltage is defined as Vcom (direct current offset) thus estimate.Even apply DC voltage from the outside, also there is the time dependence to the conversion amount in the Vcom conversion, and the conversion amount changes to the plus or minus direction according to the time mostly.In order to improve reliability, it is effective generally reducing Vcom conversion amount.
Figure 13 is the chart of the caused variation of time of expression direct current offset.In Figure 13, transverse axis express time [min], the longitudinal axis are represented direct current offset [mV].Characteristic 1311～1313 represents that respectively the frequency of drive signal is 10[Hz], 30[Hz], 100[Hz] time the variation of direct current offset.According to result shown in Figure 13 as can be known, by improving the frequency of drive signal, can reduce the conversion amount of Vcom.
Figure 14 is an example of the dielectric property of expression liquid crystal material 5CB.In Figure 14, transverse axis represents that the longitudinal axis is represented relative dielectric constant (real part of complex permittivity) to the frequency [Hz] of the drive signal of liquid crystal light modulator 1211 supplies.As shown in figure 14, be 100[Hz by the frequency that makes the drive signal that liquid crystal light modulator 1211 is supplied with] more than, thereby dielectric relaxation curve 1410 becomes fixed value.
The ionic species that contains in the liquid crystal layer is a plurality of and according to the parameter of the kind of the liquid crystal of the production environment of liquid crystal cells and use, temperature etc. and the dielectric relaxation curve is also different, but at the ratio 100[Hz of Figure 14] can to observe stationary curve be the movability that depends in the liquid crystal layer of mobile ion for the part of high frequency.And, can confirm also that by the result of direct current offset evaluation shown in Figure 13 by the frequency of drive signal being improved (for example 100[Hz]), the Vcom conversion diminishes.
Hence one can see that, an important main cause of the characteristic conversion of the liquid crystal apparatus relevant with the Vcom conversion is with the foreign ion in the liquid crystal layer of liquid crystal light modulator 1211 to be the dielectric relaxation of cause, in the drive waveforms when being contained in the consideration dielectric relaxation by making, low-limit frequency composition when just the quantity of the pulse that comprises in each frame reaches stated number is 100[Hz] more than, be the characteristic conversion of cause thereby can reduce with the mobile ion.
Thus, the foreign ion amount that reduces in the actual liquid crystal apparatus is very important, and then, be 100[Hz by the minimum frequency content that driving frequency is contained] more than, can predict can improve reliability and characteristic conversion and should through the time change.In addition, in the liquid crystal light modulator of reality, a plurality of materials that will be suitable for device characteristics mix and use, but the influence of foreign ion the example with liquid crystal material 5CB is identical as mentioned above.
As described above, according to drive unit 21, by the drive signal that contains a plurality of pulses in each frame is supplied with to liquid crystal light modulator 11, can high-frequency drive liquid crystal light modulator 11.Thus, when the virtual value of each frame that obtains regulation, can shorten continuous two recurrent intervals and the suppressor pulse waveform response.And, even also passable because do not improve the frequency of reference clock, so can realize the reduction of low consumption electrification and interference level.
And, need not with the needed clock frequency of multipolarity bring up to need above and make add first half frame that constitutes by the drive signal that contains a plurality of pulses in each frame and the polarity reversal that makes the first half frame the drive cycle of latter half frame be 10[ms] following (making the low-limit frequency that drive signal contained by the inverse definition in frame alternating polarity cycle is 100[Hz] more than), thereby the low-limit frequency that contains in the driving frequency can be improved.Therefore, can suppress the moving of mobile ion in the liquid crystal layer of liquid crystal light modulator 11, improve reliability.
Industrial utilizability
As mentioned above, drive unit involved in the present invention and optic modulating device are useful as drive unit and the optic modulating device of the modulation of carrying out light, are specially adapted to optical modulator and light adjusting device in the optical communication system.
Claims (7)
1. drive unit, its pixel portions to liquid crystal light modulator is supplied with drive signal,
Described drive unit is characterised in that,
Described drive signal is made of a plurality of frames, the virtual voltage that described frame is based on modulating data put on described liquid crystal light modulator pixel portions during,
Described drive unit has the generation mechanism that generates drive signal, and this drive signal contains a plurality of pulses in each described frame,
Described generation mechanism generates following drive signal: when the quantity of the pulse that contains in each described frame does not reach stated number, increase according to described modulating data increases the quantity of the pulse that contains in each described frame, when the quantity of the pulse that contains in each described frame reaches stated number, increase according to described modulating data increases the width of the described pulse that contains in each frame
Described drive unit has feed mechanism, and this feed mechanism is supplied with the drive signal that generates mechanism's generation by described to liquid crystal light modulator.
2. drive unit according to claim 1 is characterized in that,
In two described frames of front and back, the mode of finishing with alternating polarity generates drive signal.
3. according to claim 1 or 2 described drive units, it is characterized in that,
Described frame with the reference clock that is used to generate described drive signal, interval corresponding with the corresponding umber of pulse of the progression of described modulating data.
4. according to each described drive unit in the claim 1～3, it is characterized in that,
In described frame when applying voltage and be 0V, do not apply between described pulse the most long-term and be set in 1 * 10
-4Below [second].
5. according to each described drive unit in the claim 1～3, it is characterized in that,
In described frame when applying voltage and be 0V, do not apply between described pulse the most long-term and be set in 5 * 10
-5Below [second].
6. according to each described drive unit in the claim 1～5, it is characterized in that,
The low-limit frequency that contains in the drive signal of the inverse definition in the frame alternating polarity cycle when reaching stated number by the quantity of the pulse that contains in each described frame is more than the 100Hz.
7. a variable optical attenuator is characterized in that,
Drive unit with each described liquid crystal light modulator in the claim 1～6.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2009-101324 | 2009-04-17 | ||
| JP2009101324A JP5161832B2 (en) | 2009-04-17 | 2009-04-17 | Driving device for liquid crystal light modulation element and optical variable attenuator using the same |
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| CN101866073A true CN101866073A (en) | 2010-10-20 |
| CN101866073B CN101866073B (en) | 2014-06-11 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108919533A (en) * | 2018-08-07 | 2018-11-30 | 京东方科技集团股份有限公司 | Display panel test method and device, electronic equipment |
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| CN102866534B (en) * | 2012-10-08 | 2016-04-13 | 南京大学 | Adjustable optical attenuator |
| CN103151012B (en) * | 2013-03-06 | 2016-03-30 | 京东方科技集团股份有限公司 | Polarity reversal driving method, drive unit and liquid crystal display |
| CN103293603B (en) * | 2013-06-17 | 2016-05-11 | 南京邮电大学 | The automatically controlled variable optical attenuator of adjustable damping coefficient |
| CN104252843B (en) * | 2014-09-23 | 2016-08-24 | 京东方科技集团股份有限公司 | Pulse signal consolidation circuit, display floater and display device |
| TWI712448B (en) | 2017-03-24 | 2020-12-11 | 日商旭化成股份有限公司 | Operation method of porous membrane for membrane distillation and module for membrane distillation |
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| US20060221039A1 (en) * | 2005-04-01 | 2006-10-05 | Mitsubishi Denki Kabushiki Kaisha | Liquid crystal display device and large scale liquid crystal display system using the same |
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| CN108919533A (en) * | 2018-08-07 | 2018-11-30 | 京东方科技集团股份有限公司 | Display panel test method and device, electronic equipment |
| CN108919533B (en) * | 2018-08-07 | 2021-04-27 | 京东方科技集团股份有限公司 | Display panel testing method and device and electronic equipment |
Also Published As
| Publication number | Publication date |
|---|---|
| JP5161832B2 (en) | 2013-03-13 |
| CN101866073B (en) | 2014-06-11 |
| US8432419B2 (en) | 2013-04-30 |
| JP2010250184A (en) | 2010-11-04 |
| US20100265282A1 (en) | 2010-10-21 |
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